Geology: Deformation

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  1. Define deformation
    All changes in the original form and/or size of a rock body (folds, faults, joints).
  2. Define Stress
    The force applied to a given area
  3. Define Strain
    Changes, caused by stress, in the shape or size of a rock body.
  4. List and describe the 3 different types of stress.
    Compressional Stress: shortens/thickens a rock unit. Causes folding.

    Tensional Stress: elongates/thins a rock unit

    Shear Stress: causes adjacent parts to slide by one another; smears/tears a rock unit
  5. Tectonically, where do you expect each stress to occur?
    • Compressional - Divergent
    • Tensional - Convergent
    • Shear - Transform
  6. Discuss how temperature, confining pressure, rock type, and time all affect rock deformation.
  7. Distinguish between brittle and ductile deformation.
    If elastic limit/strength of a rock is surpassed it either flows (ductile) or fractures (brittle)
  8. Which is involved in folds? faults?
    • Ductile - folds
    • Fractures - faults
  9. List /describe each of the 5 types of folds we studied in class.  Give examples.
    Anticlines: up folded or arched rock layers(oldest material)

    Synclines: downfolds/thoughs of rock layers(youngest material)

    Monoclines: large, step-like folds in otherwise horizontal layers. Buried faults

    Dome - upward displacement

    Basin - downward displacement
  10. What stress is often involved in folding?
  11. List/describe the 5 types of faults we studied in class.
    Normal faults(tensional) - Hanging wall moves down relative to the footwall. Fault block mtns.

    Reverse and thrust faults(compressional) - Hanging wall moves up relative to footwall.

    Right/left lateral faults - Dominant displacement is horizontal, parallel to the strike of the fault.
  12. Give specific location examples for each type of fault.
  13. List and describe specific landforms associated with faulting.
    • California Coast Range
    • Basin and Range
    • Sierras
  14. Briefly discuss the origin and significance of joints.
    Joint: A fracture with no movement

    Economic mineral deposits are often emplaced along joints

    Chemical weathering is often concentrated along joints

    Highly jointed rocks are often a risk to construction projects
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Geology: Deformation
Geology Exam for Deformation
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